The areas that hold or convey stormwater runoff in extreme rain events are considered floodplain. The Federal Emergency Management Agency (FEMA) publishes maps of floodplain areas, and areas that are inundated in a 100-year storm event (that storm which has a 1% chance of occurrence in any given year) are considered regulatory floodplain. Development within the regulatory floodplain must meet certain requirements of the DuPage County Stormwater and Floodplain Ordinance and the National Flood Insurance Program administered by FEMA.
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